If you want people with RMXP to play it, just make a gamedisk.
If you want ppl without it, do this:
Find the folder your project is in. Copy the folder (it's usually in C: or D:\Program Files\Games\RPG Maker XP Postality knights version (if u have it)\games\your project) to the Desktop. Now, copy the imported files to a folder in desktop sorting graphics in one folder, and music in another. Now, replace the RTP files in the project folder with the whole RTP you find in the RMXP folder. Done it? Great. Now copy all the imported files into the RTP where it belongs WITHOUT deleting anything.
Now, goto the C:\ and find WINDOWS folder. Open it, find the system32 folder, and search for RGSS100J.dll. Found it? Copy and paste into the project folder, including a text or word document on how to install it. Delete the project file, and voila! You're done! Remember to compress it.